Force per unit area.

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Pressure inside tank while discharging water

I have two tanks, one initially fully filled with water (large tank) and the other one (smaller) is empty and has low pressure (say 0.5 bar) and the two tanks are connected from the bottom with pipe ...
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2answers
35 views

Nature of Pressure

Pressure is defined as force per unit area. Therefore, pressure = force divided by area. Since force and area are both vectors, how can we perform this division without violating the rule of vectors? ...
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1answer
123 views

Why is it not possible to use the ideal gas law to determine if the pressure changed in this situation?

I was given this question for my homework: A cylinder with a valve at the bottom is filled with an ideal gas. The vale is now opened and some of the gas escapes slowly. The valve is then closed, ...
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2answers
63 views

How much Oxygen is in ζ-phase metallic Oxygen?

I am playing with a sci-fi idea of Oxygen storage for breathing. I wonder how do some compressed forms of Oxygen compare to human-breath-Oxygen (room temperature, room pressure) in terms of density. ...
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0answers
11 views

Capillary bridge force function given volume and distance

Given two surfaces and a fluidic glue with sufficient adhesion, what is the force provided by the capillary bridge provided the cohesive properties of the glue, volume, and distance between the ...
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1answer
51 views

Managing nuclear waste [closed]

Suppose you are trying to dispose of used uranium fuel rods. Once they are cooled and contained in zirconium pods, how would one try and send those pods to the earths core? This is all hypothetical. ...
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1answer
27 views

Compute affect of a shower on density altitude

As a pilot I have a basic understanding of density altitude, how temperature affects the effective air pressure: I noticed recently that I have difficulty breathing when I take a shower in Santa ...
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1answer
55 views

$\rho g h$ and shape of container inconsistency?

The Scenario Suppose I have a cylindrical beaker and a conical flask (which cross-sectional area is bigger at the bottom), each located on an identical digital weight scale. Both of them have the ...
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2answers
50 views

Volume integral of pressure interpretation

If you have a fluid with with pressure field $p$ what is the physical significance of the the volume integral of the pressure $\int_V p dV$?
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1answer
48 views

Pressure,Pascals Law [duplicate]

Lets say that i have 2 different types of containers, one cuboidal and another one conical. and lets say both these are massless and fully contain water. **1.**In the cuboidal one the pressure ...
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1answer
290 views

Calculating flow rate of a syringe

I wanted to know how would I go about calculating the flow rate of a syringe with a metal tip that is dispensing water using a pressurized air. I have had a look on internet about this and on this ...
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1answer
63 views

why don't we consider atmospheric pressure or weight of liquid while deriving the equation of thrust in a fluid?

More specifically , when we try and prove that up thrust experienced by an liquid column inside the liquid is equal to the weight of the liquid column , I have seen it being derived like this: thrust ...
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3answers
87 views

If Gravity acts on the particles in the gas, why don't they accumulate on the lower surface and fall down?

A quantity of gas is enclosed in a metal cylinder fitted with a piston. There are very many gas molecules.The cylinder walls are thermally conducting. Now, the question...
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1answer
87 views

Bernoulli Principle and pressure function

I have read in several places now that for compressible flow the Bernoulli equation $$ \frac {v^2}{2}+ P\ + \Psi = \text{constant}$$ requires: $$P=\int {dp\over \rho(p)} $$ But I don't get ...
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0answers
60 views

Which property do the word Pressure refer to in General Theory of Relativity?

In this course by MIT Alan Guth while delivering the lecture stated " Both Pressure and Energy densities can produce gravitational fields. Negative pressure creates repulsive gravity and positive ...
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0answers
64 views

Bottle cap burst phenomenon [closed]

There is a trick you can do with a simple plastic water bottle: After putting the cap on as tight as you can, you twist the body of the bottle a few times so that it compresses the air in the bottle. ...
0
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1answer
47 views

how is the state parameter determined?

For radiation, dark energy and dust the pressure and energy density are related, respectively, by: $p=\frac{1}{3}\rho$ $p=-\rho$ $p=0$ My question is why? How does one show that this is how ...
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0answers
87 views

Air flow through a tube

During a discussion, a friend explained to me that the volume of air flowing through a tube could be increased up to the point where the air reached supersonic velocity. Presumably the pressure ...
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2answers
61 views

Pressure generated by a molecule inside an enclosure

I want to find the pressure generated by a molecule of mass $m$ and speed $v$ that is alone in an enclosure having the volume $V$. I wander if I can use the relation: $PV=mv^2/2$
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1answer
119 views

Methane under pressure [closed]

A tank is filled with liquid methane. Then it is closed. It sits in an infinite room at STP (standard temperature and pressure). (Initial temperature is not important; assume density of liquid ...
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1answer
29 views

Relative magnitudes of pressure gradient force and Coriolis force at midlatitudes

In the midlatitudes, both Coriolis and pressure gradient forces are present in the atmosphere. Can a statement be made about which one of the two forces is bigger in this region?
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2answers
668 views

Why is pressure an intensive property? [duplicate]

My teacher explained to me that we volume is an extensive property because it is additive in nature. But he also told us that pressure is an intensive property. Now according to the gas law equation ...
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8answers
158 views

Visualising gas temperature and gas pressure

Gas pressure is created when gas molecules collide with the wall of the container creating a force. Gas temperature is a measure of how fast the molecules are moving / vibrating. However, they both ...
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1answer
39 views

Why is the vapor pressure important for people that grow films in high vacuum chambers?

I don't understand what this vapor pressure is. The definition from wikipedia is unclear to me. If I look at two materials and one has a higher vapor pressure than the other, does that mean that the ...
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0answers
23 views

Can I induce draft in my chimney by heating the end of the pipe?

If I were to heat air surrounding the end of chimney cap outside could I create a difference in air pressure such that I could prevent backdraft?
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2answers
141 views

About the real reason why paper doesn't fall in HALF-FILLED inverted cup [duplicate]

I just happen to see a show about air pressure host by Brian Cox. As the link:http://imgur.com/EsRadFi shows, he flipped a half-filled water cup upside down then the paper on cup doesn't drop: It ...
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1answer
122 views

Why did my bag of chips expanded in airplane and didn't get back to normal after landing?

I bought a usual bag of chips and took the plane. In the air, it seemed that it was pretty much expanded, as if it was going to explode. I thought to myself : ok that's normal, the pressure in the ...
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1answer
206 views

Relation between pressure and velocity of a fluid

What is the relation between pressure and velocity of a fluid in a closed pipe flow? I used the Bernoulli equation in case of a pipe having non viscous fluid. The pipe is say tilted at an angle and ...
2
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1answer
74 views

Determination of radiation pressure

Consider the incidence of an electromagnetic wave on the plane $x=0$. We have that: $$f_x=\frac{dF}{dV}$$ $f_x$ is the volumic force density on the medium. My doubt is purely mathematical. I ...
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0answers
23 views

Role of rubber elasticity in the pressure inside a balloon [duplicate]

I'm just wondering if there's a pressure difference between the atmosphere and the air inside the balloon due to the rubber elasticity. A kind of analogous to the Laplace pressure in soap bubbles.
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2answers
50 views

What is the pressure exerted by air column on closed glass vessel?

Lets say we have a glass vessel initially open to atmosphere.I can understand that the pressure inside will be equal to atmospheric pressure.,But now the vessel is closed. Now will the pressure inside ...
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3answers
53 views

When deriving pressure, why do we take rebound time to be travelling time?

The derivation of the ideal gas law runs along the following lines. Imagining a container filled with some particles, by definition: $P = F/A$ $F = dp/dt$ $F_{avg} = \Delta P/ \Delta t$ If we ...
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1answer
102 views

How does pressure increase underwater?

How it is that when we go deeper in water(seas or oceans) the pressure increases, while water(generally liquids) are incompressible?
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2answers
126 views

How will hovercraft work on Mars?

The facts are: On Mars atmosphere pressure is way much lower than on Earth. To hover hovercraft blows air under itself to create air cushion. This air cushion as I understand must have enough ...
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2answers
84 views

Keeping low pressure inside a bottle

will the pressure inside a bottle remain low if I attach the bottle with a vaccum pump via a one way check valve like th following picture and then take the vacuum pump?and why?
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3answers
87 views

How does inhalation work?

In school, we learn that during inhalation, the diaphragm expands, causing air to get sucked into our lungs. You can feel this suction by putting your hand over your mouth while inhaling. Why is ...
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4answers
2k views

How is hydrostatic pressure overcome when a star is formed?

If stars are formed by the collapse of dust clouds under gravity, how is the pressure of the dust cloud overcome? As more material gathers together, gravity will increase, but pressure will also ...
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6answers
5k views

What is Pressure Energy?

While deriving Bernoulli's Theorem, our teacher said that the sum of KE, PE and Pressure Energy per unit volume remains constant at any two points. $$P + \rho g h + \frac{\rho v^2}{2} = ...
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0answers
29 views

Atmospheric Tides effect on atmospheric pressure

Regarding the atmospheric tides effect on the pressure, this answer (and the referenced sources) seem to point that such effect is very small. However, this pressure prediction graph for my hometown ...
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1answer
39 views

pulmonary physics: balloons in closed chambers

Imagine we have an expanded balloon with radius $R_1$ and an internal pressure of $+20$ atm, in an room at $0$ atm of pressure. The system is at equilibrium. Now, I drop the pressure in the room to ...
2
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2answers
49 views

I'm building a bubble pane. What can I do to reduce static pressure? [closed]

I'm building a bubble pane, just for decoration in my home, using some patio door glass panes and an aquarium air pump. Soon into my testing, I learned what static pressure is. When I fill it up, even ...
2
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0answers
89 views

Can you be your own space suit? [closed]

A few days ago a question was asked on Reddit whether or not a human could survive in space with "just enough" of a spacesuit to plug all the important holes, e.g. a face mask to plug the eyes, ears, ...
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2answers
107 views

Does the pressure at the bottom change when two liquids mix and don't mix?

My question is when these two liquids above mix and don't mix, does the pressure at the bottom change ? When they don't mix the pressure is 2hdg + 3hdg = 5hdg (d:density) But what happens when they ...
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0answers
34 views

Calculating air pressure's return to equilibrium when a chamber is unsealed

Suppose you have 1 atmosphere of pressure in a cube 1cm on a side, in an environment at 2 atmospheres of pressure, and one side of the cube has just vanished. For any given fraction R of equilibrium ...
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3answers
2k views

Why are basic physics problems neglecting to include atmospheric pressure?

The value of atmospheric pressure is 101325 Pascal, which is a large value which implies the force exerted by atmosphere is 101325 N m$^{-2}$. Surely this can not be neglected, so why is atmospheric ...
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1answer
50 views

Is Pascal's law applicable in a very large enclosed ocean?

Pascal's law states that pressure is transmitted undiminished in an enclosed static fluid. Is this law applicable, say, We apply it to a small scale so molecules push each other to transmit the ...
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2answers
228 views

Behavior of two gases in a closed container

If two ideal gases with different molecular weights (i.e. nitrogen and argon) are injected into a closed container (of any given size, but assume ~1L), what will happen over time, assuming all ...
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1answer
283 views

Pressure Calculation - Compressed Air Volume [closed]

I am trying to calculate the change in pressure in a closed pressure vessel that is being compressed. For the sake of simplicity we can consider this to be a syringe with a closed end that is being ...
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1answer
43 views

Density profile in the atmosphere, which equations to use…? [closed]

I came across the following density profile in the atmosphere: ...
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1answer
67 views

why is air pressure in force per area instead of volume?

The basic unit of Pascals, (Pa), is one Newton (N) per meter square (area). Why is this, especially for things like air pressure that deal with three dimensional space? Shouldn't something like air ...